This chapter presents a wireless interface for intra-vehicle communications (data acquisition from sensors, control, and multimedia) at 5.7 GHz. As part of the wireless interface, a RF transceiver was fabricated in the UMC 0.18 µm RF CMOS process and when activated, it presents a total power consumption of 23 mW with the voltage-supply of 1.5 V. This allows the use of only a coin-sized battery for supplying the interface. The carrier frequency can be digitally selectable and take one of 16 possible frequencies in the range 5.42-5.83 GHz, adjusted in steps of 27.12 MHz. These multiple carriers allow a better spectrum allocation and at the same time will improve the channel capacity due to the possibility to allow multiple accesses with multiple frequencies.
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Many automobile manufacturers are aiming efforts to reduce vehicle weight in order to improve the fuel economy. Also, the political, business and social need for fuel-efficient and clean vehicles is clear nowadays in many countries, where it is being demanded high environmental performance without trading-off safety, driving performance or cost (Cramer et al, 2002). Since the first Velo’s prototype presented by Karl Benz in 1894, until the modern Formula 1’s Ferrari F-60, an automobile use sensors. Ever since the introduction of the Manifold Air Pressure sensor for engine control in 1979, followed by airbag sensors in the mid-eighties. Integrated microsystems have been increasingly used throughout the vehicle, and the demand of new sensing and management applications leads undoubtedly cars to be more intelligent, and increasing the need of a networking infrastructure to connect the whole range of sensors and actuators. Thus, the system environment of an automobile is becoming more and more complex (Krueger et al, 2003). Today, an average car comprises more than 50 sensors and in the luxury segment more than 100 sensors, roughly one third (1/3) might be based on microsystem technologies. Examples of these systems are listed in Table 1 (Krueger et al, 2005). Also, while formerly one single supplier delivered all components of an ABS system or all sensors for airbag control, today the networked architecture allows merged sensor systems for different functions. Ambient intelligence, which means an environment of interacting smart devices, is opening up new information sources for the vehicle. With the growing use of bus-systems, building exclusive systems for each function is becoming more and more difficult and too expensive (Krueger et al, 2003). A present day wiring harness may have up to 4000 parts, weight as much as 40 kg, and contain more than 1900 wires for up to 4 kilometers of wiring (Ahmed et al, 2007). Thus, these networks bring serious drawbacks like reliability, maintenance and constraints if the manufacturer plans the addition of new functions. These drawbacks can be avoided with wireless transmission infrastructures. Using multi-chip-module (MCM) techniques, it is possible to assemble in the same microsystem, the sensors, radio-frequency (RF) transceiver, electronics for processing and control, memory, and an associated antenna. In the last years, the potential to use wireless interfaces in the vehicular industry became an important goal (Schoof et al 2003, ElBat et al 2006, Niu et al 2009, Leon et al 2001, Tsai et al 2007, Flint et al 2003, Li et al 2006, Niu et al 2008, Tsai et al 2007, Andreas et al 1983).